Hexahapto‐Metal Complexes of Single‐Walled Carbon Nanotubes

Abstract

We report the preparation of organometallic side‐wall complexes of single‐walled carbon nanotubes (SWNTs) under conditions, which allow the study of both mono‐ and bis‐hexahapto SWNT coordination compounds [(η6‐SWNT)Cr(CO)3, (η6‐SWNT)Cr(η6‐C6H6), (η6‐SWNT)2Cr]. The results are interpreted in terms of exohedral and endohedral binding of chromium to the SWNT sidewalls and ligand competition reactions suggest that endohedral binding provides a very stable and kinetically inert mode of organometallic bonding. We demonstrate that the electrical conductivity of SWNT thin films are significantly enhanced by side‐wall bonding to Group 6 transition metals (M = Cr, Mo, and W), which serve to reduce the inter‐carbon nanotube junction electrical resistance by the formation of SWNT interconnects [(η6‐SWNT)2M].

Enhancing conductivity of metallic carbon nanotube networks by transition metal adsorption

“…These systems are also experimentally relevant. 27 Larger decreases in the transmission function are observed in our results if there is only a Cr atom without a benzene molecule attached to a carbon ring of the nanotube. Thus, high concentrations of especially adsorbed (and possibly oxidized) Cr atoms should be avoided, e.g., by sputtering the Cr treated CNT networks.…”

“…26 Experimentally, it has been shown that transition metal (TM) atoms reduce the junction resistance efficiently. 27,28 In particular, chromium linker atoms enhance the conductance of the junction significantly. Group 6 TM atoms chromium, molybdenum, and tungsten possess six valence electrons and these atoms obtain a closed-shell structure when they bind to two carbon sidewall hexagons in CNT junctions.…”

Catalyst Residue and Oxygen Species Inhibition of the Formation of Hexahapto-Metal Complexes of Group 6 Metals on Single-Walled Carbon Nanotubes

“…Films of their Cr(SCWNT) 2 sandwich complex were observed to have an increase in C 2017, 3, 17 2 of 15 conductivity of over 100% [5]. They also reported conductivity increases for tungsten and molybdenum sandwich complexes synthesized by the same method [7].…”

“…In concept, this is an extension of doping studies where metal and non-metal species are known to intercalate within CNT bundles [5]. As part of their work, it was reported that the "Cr(CO) 3 " moiety could be coordinated to both the graphene surface and also the sidewalls of SWCNTs [5,7]. Films of their Cr(SCWNT) 2 sandwich complex were observed to have an increase in C 2017, 3, 17 2 of 15 conductivity of over 100% [5].…”

“…In a study by Haddon and co-workers, it was reported that Cr(0) is effective in increasing the conductivity of SWCNTs by the formation of Cr(SWCNT) 2 complexes that reduce the inter-nanotube junction resistance [7]. In concept, this is an extension of doping studies where metal and non-metal species are known to intercalate within CNT bundles [5].…”